As work clothes worn by people engaged in activities where they may be exposed to flames, such as firefighting and activities in electric power or chemical companies, clothes using a flame-retardant cloth have been used in the past. Such flame-retardant cloths use flame-retardant fibers such as meta-aramid fibers and para-aramid fibers. Further, it is said that such flame-retardant fibers generally have poor stretchability.
As methods for imparting stretchability to a cloth using a flame-retardant fiber, a method in which a cloth is formed using an elastic yarn together with a flame-retardant fiber (see, e.g., Patent Document 1, Patent Document 2, and Patent Document 3), a method in which a flame-retardant fiber is twisted, heat-set, and untwisted, and then a cloth is formed using the flame-retardant fiber (see, e.g., Patent Document 4, Patent Document 5, and Patent Document 6), etc., have been proposed.
However, with respect to a cloth using an elastic yarn, there have been problems with heat resistance, flame retardancy, chemical resistance, and the like. Meanwhile, with respect to a cloth using a flame-retardant fiber that has been twisted, heat-set, and untwisted, there have been problems in that its stretchability decreases during weaving, post processing, and wearing, and also the problem of increased cost.